What Noise is this??

[frankbenz]

Yesterday morning as I turned my key I heard a wierd noise, like those of a shaver or electric advertisement neon lights, coming from the small vent holes on the interior cabin lights unit above the rear view mirror. The noise will go away after a couple of second after you turn the ignition off (the same time you heard a relay click under the dash). The sound is like electric high pitch buzzing / ratling.
Anybody experience this before? Is it something that I should be worry of?
It is very annoying and makes me dizzy.
Hope somebody could tell me how to fix this
Thanks